In brief, a double whammy: as solar irradiance declines, cosmic ray influx increases both absolutely and in terms of its angle of incidence.
This means greater cloud cover as the total solar energy reaching the earth decreases, hence even larger drops in surface temperature.
Finally, large time scale solar cycles are clearly visible in carbon-14 changes in tree rings, so those cycles probably play a greater role in long-term climate change than previously thought.
Right. What you said! Thank you for distilling that. Much appeciated.
It’s my understanding that the solar wind blows most of the harmful cosmic rays away.